210 
PREPARATION OF COLLODION. 
far inferior. In wounds of considerable extent, such an ac- 
tion would evidently result in the formation of an irregular 
cicatrix, and even more serious results might follow, from 
the tension upon surrounding parts. 
At the request of those who had experienced these diffi- 
culties, I undertook a series of experiments with the view 
of producing a collodion possessing all the adhesiveness and 
transparency of the ordinary preparation, but deprived of 
the contractility, I endeavoured to combine with it a solu- 
tion of gutta-percha in chloroform ; but immediate precipita- 
tion was the result. Where the latter was in excess, the 
ether united with it, letting fall the gun-cotton : where 
collodion predominated, gutta-percha was precipitated. 
It would be -needless to mention in detail all the subse- 
sequent experiments. The terebinthinates gave the most 
satisfactory results. A few trials sufficed to show that but a 
small quantity of resin or turpentine, dissolved in recently 
prepared collodion, would totally prevent contraction, and 
increase the adhesiveness of the preparation. 
My recipe is as follows: 
Take of Prepared Cotton, Jij. 
Venice Turpentine, 3ij. 
Sulphuric Ether, §v. 
Dissolve first the cotton in the ether, add the turpentine, 
and by slight agitation complete the solution. I have pre- 
ferred Venice turpentine as the least frequently contaminated 
by mechanical impurities. 
The cotton used in these experiments was prepared ac- 
cording to Mialhe's process, by dipping carded cotton into a 
mixture of nitrate of potash and sulphuric acid: the ordinary 
commercial varieties being in all cases used. 
The above proportions should be carefully observed, as an 
excess of turpentine will cause an opacity in the film, while 
too small a quantity will not overcome the contractile 
tendency. This opacity — or, more correctly, opalescence — 
